1. Field of the Invention
The present invention relates to an information processing apparatus and an information processing method and, in particular, to an information processing apparatus and an information processing method for reducing a memory capacity used as a buffer memory for storing data in inverse wavelet transform.
2. Description of the Related Art
Joint Photographic Experts Group (JPEG) and JPEG2000, formulated by the International Organization for Standardization (ISO), are available as typical image compression methods. In accordance with the JPEG standards, discrete cosine transform (DCT) is used and, it is known that if a relatively high number of bits is assigned, good encoded and decoded images result.
Methods of segmenting an image into a plurality of bands using a filter bank including a high-pass filter and a low-pass filter and encoding the image on a per band basis have been currently actively studied. The wavelet transform encoding draws attention as a new technique superseding the DCT because the wavelet transform encoding is free from block noise at high compression rate characteristic of the DCT transform.
JPEG2000 standardized January 2001 adopts a combination of the wavelet transform and highly efficient entropy encoding (bit modeling by bit plane and arithmetic coding) and provides a marked improvement in encoding efficiency in comparison with JPEG.
In a wavelet transform process, such as the one disclosed in Japanese Unexamined Patent Application Publication No. 10-283342, image data is input and a horizontal filtering operation and a vertical filtering operation are performed on the input image data while the image data is stepwise segmented into a low-frequency component.
Image data is wavelet transformed into coefficient data (frequency component). The wavelet transformed coefficient data is inverse wavelet transformed into original image data. The inverse wavelet transform restores finally the original image by performing a synthesis filtering operation on a high-frequency component and a low-frequency component from the top segmentation level to the lowest segmentation level.
In the inverse wavelet transform, coefficient data in the middle of processing, and finally obtained image data are temporarily stored on a buffer memory.